In general, a plasma etching apparatus for etching a substrate such as a semiconductor wafer and a glass substrate for a liquid crystal display apparatus by using a plasma has been employed in a manufacturing process of semiconductor devices or the like.
The plasma etching apparatus is typically configured to include, e.g., a vacuum processing chamber; a lower electrode provided in the processing chamber, the lower electrode also serving as a mounting table on which a substrate is mounted; and an upper electrode provided to face the lower electrode. A high frequency power is supplied to the lower electrode to generate a plasma of a processing gas. Further, the plasma etching apparatus includes a focus ring provided on the lower electrode to surround a periphery of the substrate in order to improve an in-plane uniformity of processing on the substrate (see, e.g., Japanese Patent Application Pub. No. 2007-208302 and corresponding U.S. Patent Application Pub. No. 2005/0142873 A1).
In the plasma etching apparatus, when a plurality of substrates is successively subjected to the plasma etching, the temperature of the focus ring is gradually increased from a room temperature as the focus ring is exposed to the plasma. For that reason, without dealing with such change of temperature, the first substrate firstly subjected to the plasma etching has a processed state different from those of the second and following substrates subjected to the plasma etching. To prevent the occurrence of such a problem, a plasma is conventionally generated in the vacuum processing chamber while a dummy substrate is mounted on the lower electrode and the focus ring is heated by the plasma, before the start of the processing of substrates.
If a plasma is generated in the vacuum processing chamber while no dummy substrate is mounted, the surface of an electrostatic chuck provided on the lower electrode to electrostatically attract the substrate may be damaged by the plasma. Accordingly, as described above, the plasma is generated in the vacuum processing chamber while the dummy substrate is mounted on the lower electrode.
However, if the plasma is generated in the vacuum processing chamber to heat the focus ring by the plasma as described above, the focus ring and other members included in the vacuum processing chamber may be worn out. Further, if the focus ring is heated in this way, it becomes necessary to manage a frequency of using the dummy substrate or the like and provide an accommodation part (slot) for accommodating the dummy substrate.